What are library-definition problems or UPF-tolibrary mismatches, and what command reconciles a cell's actual power pins with UPF's abstract model?
From PDVerse Low-Power Physical Design Mentor Guide · pdVerse Mentor Guide
Technical Explanation
UPF's abstract supply-set model doesn't automatically know which physical pin on a real library cell corresponds to which logical supply function. set_pin_related_supply -pins -related_power_in related_ground_pin is the command that reconciles this: it explicitly ties a cell's actual physical power/ground pins to the abstract UPF supply model, which matters directly for librarydefinition problems and UPF-to-library mismatches. Related failure modes include map_retention_clamp_cell, which is not actually a valid UPF command and causes an error at load_upf if present in a UPF file, and the pin-name-matching mechanism used to auto-infer complex retention cells, which can fail to find a match and requires manual association via define_user_attribute/ set_attribute with the retention_equivalent attribute.
Architecture-level Reasoning
A cell's PG pins are a physical, library-defined fact, while UPF's supply sets are a logical abstraction — the two have to be explicitly connected somewhere, and set_pin_related_supply is the mechanism provided for doing that connection when the tool's automatic pin-name matching cannot resolve it on its own.
Step-by-step Walkthrough
1) When automatic PG-pin inference (via pin-name matching against Liberty attributes) fails to associate a cell's actual power/ ground pins with the correct UPF supply, use set_pin_related_supply -pins -related_power_in related_ground_pin to state the association explicitly. 2) For retention cells specifically, if mv.cells.infer_complex_retention_cells fails to find a match via pin-name matching, use define_user_attribute -type string classes lib_cell -name retention_equivalent followed by set_attribute ... -name retention_equivalent -value {...} to manually associate the cell. 3) Separately, watch for map_retention_clamp_cell appearing in a UPF file — it is NOT a valid UPF command and will error at load_upf if present, which is itself a form of library/UPF definitional mismatch (using a nonUPF command where a real UPF mechanism is required).
Command
set_pin_related_supply -pins {pin_list} -related_power_in related_ground_pinSwitch-by-switch
-pins: the physical pin(s) on the cell being related. related_power_in: the physical power pin associated with those
pins. -related_ground_pin: the physical ground pin associated
with those pins.Expected Result
Every physical power/ground pin on the cell correctly reconciled with the UPF abstract supply model, so downstream connectivity checks and physical implementation reflect the real cell's PG structure.
Possible Implementation Error
Placing map_retention_clamp_cell directly inside a UPF file, expecting it to behave as a normal UPF command — since it is not a valid UPF command, this causes an error at load_upf.
Likely Tool / Clp Warning
load_upf errors when map_retention_clamp_cell is present in a UPF file, since it is not a UPF command at all.
Root Cause
map_retention_clamp_cell is a separate Tcl command outside the UPF command set; using it inside a file that is parsed as UPF violates the parser's expectations regardless of the command's own validity elsewhere.
Debugging Sequence
1) If load_upf errors on an unrecognized command, check whether map_retention_clamp_cell (or another non-UPF command) was mistakenly placed inside the UPF file rather than issued as a separate Tcl command. 2) For PG-pin mismatches, check whether mv.cells.infer_complex_retention_cells succeeded via pin-name matching; if it warns of no match, use define_user_attribute/ set_attribute with retention_equivalent to manually associate the cell. 3) For general PG-pin/abstract-supply mismatches, apply set_pin_related_supply explicitly. An unresolved PG-pin-to-supply mismatch, or a load_upf failure from a misplaced non-UPF command, is a hard blocker that prevents UPF processing/PG connectivity from completing and must be fixed before proceeding.
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